Electronic equipment that utilises one or several transducers such as hearing instruments, mobile phones, medical dispensing devices etc. require that a number of electrical connections is established between signal and power terminals of the transducers and a printed circuit board housed within the electronic equipment and providing corresponding electrical contact pads or terminals. These electrical connections may be adapted to provide DC voltages and currents, digital control or data signals, digital or analogue transducer signals etc. between the printed circuit board and the transducers.
In mobile phones and hearing instrument applications, flexible transducer assemblies will typically comprise microphone(s), loudspeaker(s) or receiver(s), telecoils and, often, associated amplification circuitry which typically are required for audio signal reception/transmission and amplification.
Depending on the type of transducer assembly, it may require that two, three or even more terminals are electrically connected to the printed circuit board. These connections have previously often been provided by means of flexible leads, such as well known litz wires. However, the use of such flexible leads makes the electronic equipment unsuited for automated machine assembly. Consequently, human operators are required to carry out the process of soldering and correctly connecting the leads between corresponding terminal pairs of the transducer assemblies and the printed circuit board.
A fully silicon based sensor assembly or sensor system, which may comprise a transducer or transducer system, has recently been disclosed in assignee's pending application U.S Ser. No. 09/391,628. This sensor assembly may comprise three separate silicon substrates, that function as a transducer, an electronic signal processing circuit and a connectivity layer, respectively, assembled into a single silicon based transducer system. Even though such a silicon based transducer or sensor assembly has a number of desirable properties such as small volume, high reliability etc. it would be desirable to provide a transducer assembly that is better suited for manufacture in existing standard production equipment and processes, such as pick and place machines and re-flow soldering.
The flexible substrate transducer assembly or transducer assembly according to the present invention provides the desired ease of manufacture and may, furthermore, convey the transducer signals through a number of EMI shielded flexprint conductors and terminals or pads, thus making it possible to completely dispense with the common flexible connection leads.
U.S. Pat. No. 5,740,261 discloses a silicon based microphone having its connection terminals abutted against corresponding terminals of a flexible circuit. The silicon microphone is shielded against physical damage by a jacket that has a cylindrical top and bottom cup forming a housing that surrounds the silicon microphone. A hole in a top portion of the jacket provides an acoustic port that allows external sound pressure to enter the internal of the jacket and contact one side of a membrane of the silicon microphone. The disclosed transducer assembly is, however, not particularly well-suited for automated manufacturing. In particular, the jacket comprises a large number of relatively complex miniature mechanical parts that may require a time-consuming and manual assembly procedure.
Consequently, none of these transducer/sensor assemblies are fully satisfactory for applications in miniature or compact electronic equipment that require fabrication of large numbers of low-cost devices.